With most programs, there's some task that the program gets done (processes a packet, adds a letter to a document, compiles a file, etc.), and, in order to be working correctly, it has to do this work eventually. With graphics, in general, the program is producing images to be displayed in real time, and if it's late fewer frames are produced and the program actually does less work.
Furthermore, they sometimes run without a maximum amount of work; whenever they finish a frame, they start the next one.
Race-to-idle doesn't work at all if there is no idle state, and doesn't necessarily work the same way if being late means doing less work (possibly with a loss of output quality).